There is an on-going struggle between governments who issue genuine paper currency, and those criminals who attempt to make and pass off as genuine, worthless counterfeit imitations. In recent years, with the technological advances in printing by electronic imaging and high quality color copying processes, the task of the counterfeiter in making what appears to be genuine bank notes, has, in some respects, become much easier. Color copying machines are now available which are capable of electronically producing on virtually any kind of paper color prints of a finely detailed original image which appear visually perfect to an average person and which in fact are nearly indistinguishable on close comparison with an original. To prevent such machines from being used in the making of counterfeit currency, the United States and other governments have now begun to manufacture their paper money using various means to minimize the likelihood of counterfeiting. One of the more effective of these anti-counterfeiting measures is the printing on the bank notes of distinctive coded patterns of magnetic regions (for example, small "spots"). The various inks with which the government prints its bank notes are selectively loaded with magnetic pigment and so the identifying magnetic pattern which is printed appears visually the same as the remaining non-magnetic printing on the bank note. A unique magnetic pattern for each denomination of bank note thus serves to identify a given bank note as genuine or not and can tell its denomination. The pattern of the magnetic regions on a note is not apparent to the eye even on close inspection of a genuine bank note. As such the pattern cannot be "copied" with a copying machine. In order to recognize accurately the coded magnetic pattern printed on a bank note it is necessary to provide a detection circuit of sufficient sensitivity that it can correctly sense and properly respond to the extremely low magnetic fields provided by the printed magnetic regions of the pattern. Paper currency as its name implies is basically "paper" which is not an optimum magnetic recording medium with a backing such as tensilized polyester. Being "paper" a bank note is easily wrinkled and its printed surface degraded by numerous factors including wear and tear. Moreover, the magnetic pigments which are compatible with the printing inks used in the manufacture of paper currency are not by any means optimum for magnetic recording and reproducing. For example, the coercivity of the magnetic medium on a quality magnetic tape or computer disc may have a value of 800 Oersteds (Oe) whereas a magnetic region (spot) printed on a bank note has a coercivity of less than 100 Oe. Additionally, the remanent magnetization of a printed magnetic region on a bank note is less than one-tenth of the remanent magnetization on a quality magnetic tape. These factors plus the deteriorated physical condition of an "average" bank note after it has been in circulation for even a short time, make it extremely difficult to reliably detect and identify a pattern of magnetic regions printed on the bank note. It is therefore desirable to provide a method and an efficient electronic detection apparatus which can accurately, rapidly, and consistently detect the very low level of signals of the magnetic patterns of the printed regions on any and all bank notes (and similar articles) regardless of whether they are new, or old and worn.